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Radial JDI Passive Direct Box.

Radial Engineering JDI Duplex

4.5 4.5 out of 5, based on 5 Reviews


17th January 2012

Radial Engineering JDI Duplex by Arthur Stone

  • Sound Quality 5 out of 5
  • Ease of use 4 out of 5
  • Features 4 out of 5
  • Bang for buck 5 out of 5
  • Overall: 4.5
Radial JDI Passive Direct Box.

Radial JDI Passive Direct Box.-jdi2.jpg

Background: I use an Ibanez SR500 bass and whilst it's perfect to play, I haven't been totally happy with the tone which was lacking resolution both live and recorded; also the dynamics were uneven across strings and the fretboard. In the mix this led to an ambiguity in the soundstage and I needed a lot of top end to bring definition whilst boosting the bass meant wooliness. Things improved after DI'ing the bass through a BAE1073mpf (which passed through the output transformer but not the input transformer)...the tone was there...a healthy ringing warmth - but still the lack of definition and uneveness of dynamics.
After reading up at I reckoned I needed a passive DI - I nearly bought a cheap one, but decided to save up for a Radial JDI. It arrived this morning.

Hardware: The first thing I noticed as I unpacked it was the weight (720g)...very solid; this acts like an anchor with the non-slip rubberised base. The folded-steel design is ergonomic and there are no sharp edges to snag cables. The enamel finish is quality with clear legends; the push-buttons latch well and the insert sockets are tightly secured to the chassis. As the JDI a passive unit there is no batteries or external power needed.
Radial JDI Passive Direct Box.-jdi3.jpgRadial JDI Passive Direct Box.-jdi4.jpg

In Use: The weight is a well-judged balance between stability and portability, it's a solid base for the cable and doesn't drag around easily, it's set and forget. I plugged in an active bass (Ibanez SR500) to the JDI input; then a short XLR from the JDI output into the mic input on the BAE and added 40dB of gain (@1200ohms).
I was blown away from the start - it sounded 'peachy' (sorry!). The tone was very pleasant, still the harmonics but no harshness; the resolution of the tone, the shape of it, was incredible...very 3D (and I'm looking forward to mixing bass now); the articulation of dynamics seemed to have been improved too - there was more evenness across strings and frets. Basically it sounded like one guitar rather than 4 different ones.

On electro-acoustic guitar the JDI performed just as well as bass...same peachiness of tone and smoothing of harsh harmonics with added 3Dness.
I tried a passive electric guitar too and was impressed...better than any other DI input I have - the fact that the JDI is passive didn't adversely affect the tone...maybe a little bit darker but certainly full bodied.
'Musical' really does apply here; it's as if the JDI is an instrument itself.

Conclusion: This is great bang-for-buck for your signal path. It sounds superb. Excellent design and build quality. I'd thoroughly recommend the JDI for anyone who wants to improve their guitar tone and resolution.

Radial Engineering JDI & J48

17th January 2012

Radial Engineering JDI Duplex by GoldMember

  • Sound Quality 4 out of 5
  • Ease of use 5 out of 5
  • Features 4 out of 5
  • Bang for buck 4 out of 5
  • Overall: 4.25
Radial JDI Passive Direct Box.

the Dual latest MK, has great sound...
adds jensen transformer sound too electric guitars & electric bass...
synths too.

its great if you want to connect the instrument to any mic-pre.

some highend mic-pres have a DI input,
but most are transformerless, "bypass the input transformer of the mic-pre", if that mic-pre has one.

some mic.pre DI input is lower quality, or is too clean... this will solve the problem.

this JDI adds analog magic without much coloration.

i think it sounds sweeter than Whirlwind IMP-2.

18th March 2012

Radial Engineering JDI Duplex by Klemi

  • Sound Quality 4 out of 5
  • Ease of use 5 out of 5
  • Features 5 out of 5
  • Bang for buck 4 out of 5
  • Overall: 4.5
Radial JDI Passive Direct Box.

I record bass and guitar through Presonus FP10 firewire interface, I use Reaper DAW on Windows 7 64-bit, all free plugins + Overloud TH2 for guitars (and sometimes bass). FP10 has 8 mic inputs, 2 being instrument and 6 being line inputs.
I use KRK RP6 G2 monitors.
I play G&L L-2500 Tribute bass and Suhr Pro Series S1 guitar. I also have a Ampeg Rocket Bass B-100R combo bass amp.
My setup is actually pretty decent for home studio and my "needs".
I do this for hobby, I am not a professional, this is more or less for fun. My music gets used by my friend for his non commercial videos and some other projects.

One link: Sailing [2005 - 2010] (Dalmatia, Istra, Kornati, Croatia) - YouTube

This is old stuff, I am now older, wiser.... And this is in pre-DI times!

Why JDI:

It's passive - no extra power required
It has ground lift - I can record through my bass amp and NOT have hum.
I can record clean signal and play through amp at the same time.
It's build like a tank. Once you see and lift this box, you know you're dealing with a serious product. Price tag might lead you to same conclusion.
Features and feel of it in general - you can feel that a lot of effort was put into designing this box - everything is marked well, knobs and guts are protected by the metal shell, It's remarkable you don't need a weapon license on this DI.


First of all - I found out I have to crank my input few dBs higher with JDI in the chain. Might be the change in impedance or the nature of the passive DI.
What I get is sound with more definition in bass and in high end, bass sounds more solid and guitars sound more focused. TH2 is a great guitar amp sim, but JDI makes it even better. It seems that cranking the input up has one more positive effect - I get better sustain
My feeling is this box puts the signal through it's transformer, cleaning all the EM and radio interference on the way, leaving you with a good raw, base signal with plenty headroom.

2nd April 2012

Radial Engineering JDI Duplex by soundmark

  • Sound Quality 5 out of 5
  • Ease of use 5 out of 5
  • Features 4 out of 5
  • Bang for buck 4 out of 5
  • Overall: 4.5
Radial JDI Passive Direct Box.

I am consistantly amazed by this Direct Box. I have 5 of them and am so happy with the tone and consistancy of the box. It is truly world-class in every way. I have used so many direct boxes, and these are truly special. An engineers dream.

25th May 2017

Radial Engineering JDI Duplex by Davemac

  • Sound Quality 4 out of 5
  • Ease of use 5 out of 5
  • Features 5 out of 5
  • Bang for buck 5 out of 5
  • Overall: 4.75
Radial JDI Passive Direct Box.

Radial JDI vrs J48 vrs LRBaggs ParaEQ Review

Guitar - 1935 Gibson L00
Pickup - LRBaggs M1 (passive model, no battery)
Amp - AER Compact Mobile (Mic input, EQ flat, Master Vol @ 12 o'clock)

Short answer:

Radial JDI easily best in show, lowest noise, silent switches, most apparent polarity reversal effect and warmest, truest sound, by far. Whether it be finger picking or flat out American Pie fireside strumming, the JDI killed the other two for balanced clarity, warmth and pleasing saturation. I was surprised!

LRBaggs ParaEQ: a surprising noise floor and 'thump' noise on 'invert' switch and a colossal capacitor discharge noise if you disturb the XLR plug connection because you were thumping your foot too close to the unit mid solo.
Middle guy in regards to the output sonics, warmer than the J48 but still a bit brittle compared to the JDI.

J48: epic fail on switching noise and worst score on noise floor. Sonically the most sizzly and hawkish of transformers and least pleasing to my ear. Sorry Radial J48

Result: returning the J48, retiring the LRBaggs ParaEQ to 'backup' status and super stoked to be taking on the much better sounding and more fool proof passive Radial JDI even though I use a passive LRBaggs M1 pickup. I was surprised at that too.

Word: why do all these units make 'snow' or 'white' noise of various levels and characteristics with the JDI making the least and the J48 the most? And maybe with the JDI lower passive output you get to work your amp a little more into the pleasing saturation and warming range of the amps circuitry?

Long Answer:

Setup and volume balancing of DI's

I wanted to get a feel for the balanced mic level outputs of the DI's which all have slightly different gain structures. To get the best relatively equal volume between the three DI's required a little trial and error with the amp channel input gain settings and the J48 -15 dB pad, ie;

amp channel input gain: 1 o'clock

amp channel input gain: 11 o'clock with J48 -15 dB switched in

LRBaggs (DI gain and volume set to 12 o'clock)
amp channel input gain: 8 o'clock

Not ideal that the amp input strip needs to be driven between 8 o'clock and 1 o'clock between DI's but keeping the master at 12 o'clock felt like a better reference point compromise.

Background Noise once XLR connected

What became immediately apparent was the introduction of unique 'snow' or 'white' noise for all three units once the XLR connection is made between the amp and the DI.

This was surprising to me and even more so being that the noise level and character was evident regardless of whether the phantom power was on or off and if the instrument input was muted or open.

I compared the noise floor introduced by a M88 (Beyerdynamic) mic to hear what noise it made and that was minuscule by comparison.

When the guitar is lined directly into the instrument input strip of the amp (rather than via the mic input using the DI's XLR feeds) there is practically zero noise introduced and for this reason I am circumspect about all three of these DI's as clean noise-free signals for mic level balanced output.

If I was using the AER as a stage amp, I would experiment with the noise issue switching between the DI XLR output verses the inbuilt AER XLR DI output to find the quietest solution.

I wasn't expecting this kind of noise and at the qualitative levels noticed;

JDI: lowest level (but still audible)

J48: highest level (with some RF?)

LRBaggs: moderate level

Noiseless Switches ?!

Of big importance to me is my soundcheck process. Keeping my stage sound clear and clean and being able to confidently soundcheck my signal path, pads, ground lifts and polarity all makes a huge difference to me. And it makes a huge difference for the FOH and Monitor folks too.

In the past I had been a little annoyed that my LRBaggs Para EQ makes a modest bump noise when I switch polarity. What increased my annoyance with the ParaEQ was if you stomped the stage too close to the DI unit, one of the XLR pins looses contact and that almighty capacitor discharge thump tries to kill the PA. This has happened once too many times and this is why I went looking into Radial units.

It must be a build flaw in the LRBaggs ParaEQ that the top location of the XLR output plug means that the cable is immediately torqued or bent once leaving the unit enroute to the stage box, making the pin connections more vulnerable to loosing contact and making the worst of noises.

But what really shocked me was the racket that the Radial J48 makes when any of the various switches were used (pad, polarity, merge and ground lift) under load when open to the PA and was a real deal breaker for me. The Radial J48 manual mentions 'silent' switches ... well they weren't for me, sorry Radial (I had two units shipped to me hoping this was a one off problem and the supplier even tested the rest of his stock, but alas), the J48 fell out of the running for me at this point.

I know I know, you're supposed to mute the input when switching things up on the DI but have you ever sound checked like that and who puts a mute switch after the XLR out anyways? "Hey monitors, I'll just flick the phase on the DI to see if we can't lose some of that stage bottom end, ...but first can you mute because my phase switch sends 1000 dB of crap down your line, and then can you un-mute me and we can try and remember the difference between the two and then we'll do the same with the pad switch and then the same if we need to lift the ground, okay?". At that point the monitor person have lost confidence in my gear and my gig and the FOH reaches for the 'suck' button on my guitar line.

On the sunny side for Radial, the JDI switches are silent, bravo!

The Sound

The Radial JDI by far had the most pleasing sound both for fingerpicking and straight up strumming. There was none of that brittle sizzle or hawkish upper mids to contend with and I have 'tuned' my M1 pickup by adjusting the poles so I know what my sound should be and the JDI was easily the warmest and truest to my ears.

The LRBaggs came in second, it had that 'bright'ish' sound I kind of hate by comparison given everything was set flat. Active DI's definitely have if not a sound but a 'quality' of more urgent crispy tops. What was surprising to me is that I have been real happy with the LRBaggs ParaEQ for a decade, but this simple A B test totally schooled me.

Sorry to go against the tide of popular opinion here but the Radial J48 was an epic disappointment by comparison. Just like my bias being wedded to the ParaEQ for all these years, i wanted the Radial J48 to rule, but the noise floor, the noisy switches and overly harsh upper mids and tops just turned me off. I tested two and had the supplier check his stock as well, but the verdict was absolute.

And that was my qualitative 'ears only' Radial JDI vrs J48 vrs LRBaggs ParaEQ review.I vrs J48 vrs LRBaggs ParaEQ Review[/B]

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